|Abstract from DBPedia||
The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System.About three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron. The Sun is a G-type main-sequence star (G2V) based on its spectral class, and is informally referred to as a yellow dwarf. It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. It is thought that almost all stars form by this process. The Sun is roughly middle-aged: it has not changed dramatically for more than four billion years, and will remain fairly stable for more than another five billion years. After hydrogen fusion in its core has stopped, the Sun will undergo severe changes and become a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury, Venus, and possibly Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. The synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today.
太陽（たいよう、英: Sun、羅: Sol）は、銀河系（天の川銀河）の恒星の一つである。人類が住む地球を含む太陽系の物理的中心であり、太陽系の全質量の99.86%を占め、太陽系の全天体に重力の影響を与える。 太陽は属している銀河系の中ではありふれた主系列星のひとつで、スペクトル型はG2V（金色）である。推測年齢は約46億年で、中心部に存在する水素の50%程度を熱核融合で使用し、主系列星として存在できる期間の半分を経過しているものと考えられている。 また太陽が太陽系の中心の恒星であることから、任意の惑星系の中心の恒星を比喩的に太陽と呼ぶことがある。